1. Field of the Invention
The present invention relates to a vehicular cooling system having a heat source, such as a fuel cell or an engine, and a radiator for radiating heat of coolant heated by the heat source. More specifically, the present invention relates to a vehicular cooling system having a selector switch such as a thermostat for switching the coolant circulation path.
2. Description of Background Art
In recent years, there have been developed fuel cell vehicles in which electric power generated by a fuel cell system is supplied to a motor and wheels are driven by the motor. In the above-mentioned fuel cell system, electric power is generated by chemical reaction between hydrogen as fuel gas and oxygen as reactant gas in a fuel cell stack (hereinafter, simply referred to as the “fuel cell”). Here, oxygen is taken in from the air through a compressor, and hydrogen is supplied from a high-pressure fuel cylinder.
A fuel cell generates heat through chemical reaction. For efficient power generation, excess heat must be radiated away to cool the fuel cell to keep it within an appropriate temperature range. For efficient heat radiation, such as a fuel cell vehicle disclosed in JP-A No. 2005-119600, for example, a water-cooling type cooling system may be employed to cool the fuel cell and radiate heat out of the heated cooling water by a radiator.
In the fuel cell vehicle disclosed in JP-A No. 2005-119600, a reservoir tank is provided above the fuel cell, and the reservoir tank is provided with a degassing mechanism capable of automatically removing air entering the coolant.
Although the reservoir tank described in JP-A No. 2005-119600 above allows removal of air entering the pipeline in the cooling system, it is difficult to release air entering the fuel cell to the pipeline or the reservoir tank. Accordingly, the air in the fuel cell may remain in an upper part of the fuel cell for a long time, resulting in deterioration in cooling efficiency.
Further, when the temperature is below an appropriate temperature and a warm-up is required, the circulation path for coolant may be switched by a thermostat (see, for example, JP-A No. H11-93666) to allow the coolant to be bypassed without passing through the radiator, thereby promoting temperature rise.
In a fuel cell motorcycle, a large number of components such as a fuel cell, a supercharger, and a humidifier must be disposed within a narrow confined space. Accordingly, it is desirable that routing of the pipe line between these components can be easily performed so as not to interfere with the layout of other components. It is desirable that not only the pipe line of a supply system for fuel gas and reactant gas to which a supercharger, a humidifier, and so on are connected, but also the pipe line in the cooling system be disposed in an appropriate manner so as not to affect the arrangement of other components.
Further, typical motorcycles or four-wheeled vehicles are also mounted with a cooling system having an engine and an electric motor as heat sources and a radiator for cooling these components. Since these vehicles do not necessarily have a large engine room, the pipe line arrangement in the cooling system must be performed in an appropriate manner.
The present invention has been made in view of the above-mentioned problem, and accordingly it is an object of the present invention to provide a cooling system for a fuel cell vehicle which allows efficient removal of air entering a fuel cell. It is a further object of the present invention to provide a vehicular cooling system which allows easy pipe line routing and an increase in the freedom of the layout of components.